This invention relates to data storage apparatus and is particularly, although not exclusively, concerned with storage apparatus for microprogram data (i.e. sequences of microinstructions).
It is often required to read a series of data items (e.g. microinstructions) in rapid succession. This implies, among other things, that the circuits for generating addresses for the data store should be positioned in close physical proximity to the store, so as to reduce the effects of propagation delays. It may, for example, be possible to locate the address generating circuits on the same printed circuit board as the store. However, if it is desired to extend the store, it may not be physically possible to put an additional store on the same circuit board. The additional store must therefore be located on another circuit board remote from the first store and the address generating circuit, and as a result the access time for the additional store is increased.
The object of the present invention is to alleviate this problem.